Boston Celtics' Kevin Garnett (5) and Mickael Pietrus, rear, of France, block a drive to the basket by Miami Heat's LeBron James (6) during the first half of Game 2 in their NBA basketball Eastern Conference finals playoffs series, Wednesday, May 30, 2012, in Miami. (AP Photo/Lynne Sladky)— AP

Boston Celtics' Kevin Garnett (5) and Mickael Pietrus, rear, of France, block a drive to the basket by Miami Heat's LeBron James (6) during the first half of Game 2 in their NBA basketball Eastern Conference finals playoffs series, Wednesday, May 30, 2012, in Miami. (AP Photo/Lynne Sladky)
/ AP

Miami Heat's Udonis Haslem (40) and LeBron James (6) pressure Boston Celtics' Brandon Bass (30) as he drives to the basket during the second half of Game 2 in their NBA basketball Eastern Conference finals playoffs series, Wednesday, May 30, 2012, in Miami. (AP Photo/Lynne Sladky)— AP

Miami Heat's LeBron James (6) and Dwyane Wade (3) gesture after the Boston Celtics scored during the second half of Game 2 in their NBA basketball Eastern Conference finals playoffs series, Wednesday, May 30, 2012, in Miami. (AP Photo/Lynne Sladky)
/ AP

MIAMI 
Back and forth they went in overtime, Rajon Rondo and the Miami Heat.

Rondo scored. The Heat answered. Then again. And again.

Eventually, Rondo missed, one of the rare times he didn't deliver on an unforgettable night. Moments later, the Heat took the lead for good, finally able to close out a wild Game 2 of the Eastern Conference finals.

LeBron James scored 34 points and grabbed 10 rebounds, Dwyane Wade scored eight of his 23 points in the extra session and the Heat rallied from 15 down to beat the Boston Celtics 115-111 on Wednesday night - taking a 2-0 lead in the series by pulling off the biggest comeback in franchise postseason history.

"One of the best games I've played in, win or lose," Heat forward Shane Battier said. "It's easier said when you win - but it's unbelievable."

Rondo scored all 12 of Boston's points in overtime, capping a 44-point, 10-assist, eight-rebound effort in which he played every second of a 53-minute game. The Heat expected Boston's best - and the Celtics didn't disappoint, yet still head home for Game 3 on Friday night facing a deficit no Boston team has rallied from to win a series since 1969.

"Listen, we played terrific," Celtics coach Doc Rivers said. "I told them, we played extremely hard. I thought we played with great heart tonight, but I didn't think we played smart all the time. And there's things we can absolutely fix, and we'll do that. We'll be ready for Friday."

Mario Chalmers scored 22 for the Heat, who took 47 free throws - 24 by James - to Boston's 29.

"This group had resolve," Wade said of the Celtics. "They came out and played a great game. It was physical early. They brought the game to us. That can't happen. We used our crowd and the energy to get back into the game and we had to play better."

Paul Pierce scored 21 points, Kevin Garnett added 18 and Ray Allen 13 for Boston. Rondo finished 16 of 24 from the floor, 10 of 12 from the foul line and made both his 3-point tries.

"He showed why he's one of the best point guards in this league," Chalmers said.

Rondo shrugged off his night.

"We lost," Rondo said. "Simple as that."

Allen's 3-pointer with 34.3 seconds left tied the game at 99-all. James missed two shots, first a layup - he got the rebound of his own miss - and then a jumper on the final possession of regulation, and to overtime they went.

"We had to do it the tough way," Heat coach Erik Spoelstra said.

The Heat had come back to win from 14 points down in playoff games twice before, first in Game 6 of the 2006 NBA finals - their title clincher - and again last season against Philadelphia.

And this one was slipping away, more than once. James missed two free throws 21 seconds into overtime, and Miami looked in trouble, especially since Rondo was simply taking over.